Method and apparatus for re-routing calls in a packet network during failures

ABSTRACT

Method and apparatus for re-routing a call in a packet network during failures is described. In one example, a failure condition is detected for a destination endpoint for the call. At least one alternative endpoint address is identified from an alternative routing plan registered with the packet network in response to the failure condition. For example, various alternative routing plans may be registered with the packet network and stored in a database. Each of the alternative routing plans may include alternative endpoint address data for a plurality of endpoint devices. The database may be queried using the destination endpoint as an index value and the at least one alternative endpoint address may be retrieved. The call is then routed to the at least one alternative endpoint address.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate totelecommunications systems and, more particularly, to a method andapparatus for re-routing calls in a packet network during failures isdescribed.

2. Description of the Related Art

Generally, telecommunications systems provide the ability for two ormore people or machines (e.g., computerized or other electronic devices)to communicate with each other. A telecommunications system may includevarious networks for facilitating communication that may be generallyorganized into packet networks and circuit-switched networks. Exemplarypacket networks include internet protocol (IP) networks, asynchronoustransfer mode (ATM) networks, frame-relay networks, and the like. Anexemplary circuit-switched network includes a plain old telephone system(POTS), such as the publicly switched telephone network (PSTN).

Telephony service providers typically offer services to enterprises thataccess the services through nodal endpoints on the customer premises.Presently, when these nodal endpoints experience outages (i.e., when thenodal endpoints fail), calls to these endpoints are blocked. These callsare blocked regardless of the existence of alternative active endpointsfor reaching the user of the failed device. Accordingly, there exists aneed in the art for a method and apparatus that re-routes calls in apacket network during failures.

SUMMARY OF THE INVENTION

Method and apparatus for re-routing a call in a packet network duringfailures is described. In one embodiment, a failure condition isdetected for a destination endpoint for the call. At least onealternative endpoint address is identified from an alternative routingplan registered with the packet network in response to the failurecondition. For example, various alternative routing plans may beregistered with the packet network and stored in a database. Each of thealternative routing plans may include alternative endpoint address datafor a plurality of endpoint devices. The database may be queried usingthe destination endpoint as an index value and the at least onealternative endpoint address may be retrieved. The call is then routedto the at least one alternative endpoint address.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a block diagram depicting an exemplary embodiment of acommunication system in accordance with the invention;

FIG. 2 is a block diagram depicting an exemplary configuration of thecommunication system of FIG. 1 in accordance with the invention;

FIG. 3 is a flow diagram depicting an exemplary embodiment of a methodfor routing a call in a packet network in accordance with one or moreaspects of the invention; and

FIG. 4 is a block diagram depicting an exemplary embodiment of acomputer suitable for implementing the processes and methods describedherein.

DETAILED DESCRIPTION

To better understand the present invention, FIG. 1 illustrates anexample network, e.g., a packet network such as a voice-over-internetprotocol (VoIP) network related to the present invention. Exemplarypacket networks include internet protocol (IP) networks, asynchronoustransfer mode (ATM) networks, frame-relay networks, and the like. An IPnetwork is broadly defined as a network that uses Internet Protocol toexchange data packets. Thus, a VoIP network or a SoIP (Service overInternet Protocol) network is considered an IP network.

In one embodiment, the VoIP network may comprise various types ofcustomer endpoint devices connected via various types of access networksto a carrier (a service provider) VoIP core infrastructure over anInternet Protocol/Multi-Protocol Label Switching (IP/MPLS) based corebackbone network. Broadly defined, a VoIP network is a network that iscapable of carrying voice signals as packetized data over an IP network.The present invention is described below in the context of anillustrative VoIP network. Thus, the present invention should not beinterpreted to be limited by this particular illustrative architecture.

Referring to FIG. 1, the customer endpoint devices can be either TimeDivision Multiplexing (TDM) based or IP based. TDM based customerendpoint devices 122, 123, 134, and 135 typically comprise of TDM phonesor Private Branch Exchange (PBX). IP based customer endpoint devices 144and l45 typically comprise IP phones or PBX. The Terminal Adaptors (TA)132 and 133 are used to provide necessary interworking functions betweenTDM customer endpoint devices, such as analog phones, and packet basedaccess network technologies, such as Digital Subscriber Loop (DSL) orCable broadband access networks. TDM based customer endpoint devicesaccess VoIP services by using either a Public Switched Telephone Network(PSTN) 120, 121 or a broadband access network via a TA 132 or 133. IPbased customer endpoint devices access VoIP services by using a LocalArea Network (LAN) 140 and 141 with a VoIP gateway or router 142 and143, respectively.

The access networks can be either TDM or packet based. A TDM PSTN 120 or121 is used to support TDM customer endpoint devices connected viatraditional phone lines. A packet based access network, such as FrameRelay, ATM, Ethernet or IP, is used to support IP based customerendpoint devices via a customer LAN, e.g., 140 with a VoIP gateway androuter 142. A packet based access network 130 or 131, such as DSL orCable, when used together with a TA 132 or 133, is used to support TDMbased customer endpoint devices.

The core VoIP infrastructure comprises of several key VoIP components,such the Border Element (BE) 112 and 113, the Call Control Element (CCE)111, and VoIP related servers 114. The BE resides at the edge of theVoIP core infrastructure and interfaces with customers endpoints overvarious types of access networks. BEs may also be referred to as “edgecomponents”. A BE is typically implemented as a Media Gateway andperforms signaling, media control, security, and call admission controland related functions. The CCE resides within the VoIP infrastructureand is connected to the BEs using the Session Initiation Protocol (SIP)over the underlying IP/MPLS based core backbone network 110. The CCE istypically implemented as a Media Gateway Controller and performs networkwide call control related functions as well as interacts with theappropriate VoIP service related servers when necessary. The CCEfunctions as a SIP back-to-back user agent and is a signaling endpointfor all call legs between all BEs and the CCE. The CCE may need tointeract with various VoIP related servers in order to complete a callthat require certain service specific features, e.g. translation of anE.164 voice network address into an IP address.

For calls that originate or terminate in a different carrier, they canbe handled through the PSTN 120 and 121 or the Partner IP Carrier 160interconnections. For originating or terminating TDM calls, they can behandled via existing PSTN interconnections to the other carrier. Fororiginating or terminating VoIP calls, they can be handled via thePartner IP carrier interface 160 to the other carrier.

In order to illustrate how the different components operate to support aVoIP call, the following call scenario is used to illustrate how a VoIPcall is setup between two customer endpoints. A customer using IP device144 at location A places a call to another customer at location Z usingTDM device 135. During the call setup, a setup signaling message is sentfrom IP device 144, through the LAN 140, the VoIP Gateway/Router 142,and the associated packet based access network, to BE 112. BE 112 willthen send a setup signaling message, such as a SIP-INVITE message if SIPis used, to CCE 111. CCE 111 looks at the called party information andqueries the necessary VoIP service related server 114 to obtain theinformation to complete this call. If BE 113 needs to be involved incompleting the call; CCE 111 sends another call setup message, such as aSIP-INVITE message if SIP is used, to BE 113. Upon receiving the callsetup message, BE 113 forwards the call setup message, via broadbandnetwork 131, to TA 133. TA 133 then identifies the appropriate TDMdevice 135 and rings that device. Once the call is accepted at locationZ by the called party, a call acknowledgement signaling message, such asa SIP-ACK message if SIP is used, is sent in the reverse direction backto the CCE 111. After the CCE 111 receives the call acknowledgementmessage, it will then send a call acknowledgement signaling message,such as a SIP-ACK message if SIP is used, toward the calling party. Inaddition, the CCE 111 also provides the necessary information of thecall to both BE 112 and BE 113 so that the call data exchange canproceed directly between BE 112 and BE 113. The call signaling path 150and the call data path 151 are illustratively shown in FIG. 1. Note thatthe call signaling path and the call data path are different becauseonce a call has been setup up between two endpoints, the CCE 111 doesnot need to be in the data path for actual direct data exchange.

Note that a customer in location A using any endpoint device type withits associated access network type can communicate with another customerin location Z using any endpoint device type with its associated networktype as well. For instance, a customer at location A using IP customerendpoint device 144 with packet based access network 140 can callanother customer at location Z using TDM endpoint device 123 with PSTNaccess network 121. The BEs 112 and 113 are responsible for thenecessary signaling protocol translation, e.g., SS7 to and from SIP, andmedia format conversion, such as TDM voice format to and from IP basedpacket voice format.

FIG. 2 is a block diagram depicting an exemplary configuration of thecommunication system of FIG. 1 in accordance with the invention. In thepresent embodiment, an endpoint device 202 is in communication with thecore network 110 through an access network 204 and a border element 206.Endpoint devices 216 and 218 are in communication with the core network110 through an access network 214 and a border element 208. Theoriginating endpoint devices 202 and the terminating endpoint devices208 may comprise any of the customer endpoint devices described above(e.g., TDM devices, IP devices, etc.). The access networks 204 and 214may comprise any of the access networks described above (e.g., PSTN,DSL/Cable, LAN, etc). In the present example, the endpoint device 202attempts to establish a call to the endpoint device 216. Thus, theendpoint device 202 is referred to as the originating endpoint device,and the endpoint device 216 is referred to as the destination endpointdevice.

For each call requested by the originating device 202, the call setupprocess described above is performed. In the present example, assumethat the destination endpoint device 216 has failed (e.g., thedestination endpoint device 216 has ceased to function, has lost power,or is otherwise unable to perform its intended function). The call setupmessage transmitted by the BE 208 towards the destination endpointdevice 216 is not acknowledged due to the failure. As such, a failurecondition is detected for the destination endpoint device 216. Thefailure condition may be detected by the BE 208, the CCE 111, or both(referred to as the “detecting network element”).

The destination endpoint device 216 may be unavailable for other reasonsthan a failure. For example, the destination endpoint device 216 may beunavailable to receive the call due to a busy condition or a no answercondition. However, the detecting network element is configured todetermine whether the unavailability of the destination endpoint device216 is due to a failure condition or a busy/no answer condition. Forexample, the destination endpoint device 216 may respond to the callsetup message with a message indicative of the busy/no answer condition,which is received by the detecting network element. In contrast, if thedestination endpoint device 216 has failed, no such busy/no answermessage is received, which is indicative of a failure condition. In thismanner, the detecting network element is configured to distinguishbetween a busy/no answer condition and a failure condition.

Having detected a failure condition for the destination endpoint device216, the detecting network element informs an application server 210.The application server 210 is coupled to a database 212. The database212 is configured to store various alternative routing plans fordifferent endpoint devices. Each alternative routing plan may comprisealternative endpoint address data for each of a plurality of endpointdevices. For example, an enterprise may register an alternative routingplan with the network for its endpoint devices. The application server210 queries the database 212 using the destination endpoint address asan index value to identify at least one alternative endpoint address forthe endpoint device(s) 218 (“alternative endpoint device(s)”). Theapplication server 210 then forwards the alternative endpoint addressdata to the detecting network element. The detecting network elementthen re-routes the call to one or more of the alternative endpointdevice(s). In this manner, when the destination endpoint device 216 hasfailed, calls to the device are re-routed to alternative device(s)instead of being blocked.

FIG. 3 is a flow diagram depicting an exemplary embodiment of a method300 for routing a call in a packet network in accordance with one ormore aspects of the invention. The method 300 begins at step 301. Atstep 302, a determination is made whether the destination endpoint forthe call is unavailable. If not, the method 300 proceeds to step 312,where the normal call setup process is performed. The method then endsat step 399. Otherwise, the method 300 proceeds to step 304. At step304, a determination is made whether the unavailability of thedestination endpoint is due to an error condition. If not, the method300 proceeds to step 314, where the normal process for handling abusy/no answer condition is performed (e.g., a busy signal is returnedto the originating device in response to a busy condition, a no answermessage is returned to the origination device in response to a no answercondition). The method 300 then ends at step 399. Otherwise, the method300 proceeds to step 306.

At step 306, a failure condition for the destination endpoint is deemedto be detected. At step 308, at least one alternative endpoint addressis identified from an alternative routing plan registered with thepacket network in response to the failure condition. At step 310, thecall is routed to the at least one alternative endpoint address. Themethod 300 then ends at step 399.

FIG. 4 is a block diagram depicting an exemplary embodiment of acomputer 400 suitable for implementing the processes and methodsdescribed herein. The computer 400 includes a central processing unit(CPU) 401, a memory 403, various support circuits 404, and an I/Ointerface 402. The CPU 401 may be any type of microprocessor known inthe art. The support circuits 404 for the CPU 401 include conventionalcache, power supplies, clock circuits, data registers, I/O interfaces,and the like. The I/O interface 402 may be directly coupled to thememory 403 or coupled through the CPU 401. The I/O interface 402 may becoupled to various input devices 412 and output devices 411, such as aconventional keyboard, mouse, printer, display, and the like.

The memory 403 may store all or portions of one or more programs and/ordata to implement the processes and methods described herein. Althoughone or more aspects of the invention are disclosed as being implementedas a computer executing a software program, those skilled in the artwill appreciate that the invention may be implemented in hardware,software, or a combination of hardware and software. Suchimplementations may include a number of processors independentlyexecuting various programs and dedicated hardware, such as ASICs.

The computer 400 may be programmed with an operating system, which maybe OS/2, Java Virtual Machine, Linux, Solaris, Unix, Windows, Windows95,Windows98, Windows NT, and Windows2000, WindowsME, and WindowsXP, amongother known platforms. At least a portion of an operating system may bedisposed in the memory 403. The memory 403 may include one or more ofthe following random access memory, read only memory, magneto-resistiveread/write memory, optical read/write memory, cache memory, magneticread/write memory, and the like, as well as signal-bearing media asdescribed below.

An aspect of the invention is implemented as a program product for usewith a computer system. Program(s) of the program product definesfunctions of embodiments and can be contained on a variety ofsignal-bearing media, which include, but are not limited to: (i)information permanently stored on non-writable storage media (e.g.,read-only memory devices within a computer such as CD-ROM or DVD-ROMdisks readable by a CD-ROM drive or a DVD drive); (ii) alterableinformation stored on writable storage media (e.g., floppy disks withina diskette drive or hard-disk drive or read/writable CD or read/writableDVD); or (iii) information conveyed to a computer by a communicationsmedium, such as through a computer or telephone network, includingwireless communications. The latter embodiment specifically includesinformation downloaded from the Internet and other networks. Suchsignal-bearing media, when carrying computer-readable instructions thatdirect functions of the invention, represent embodiments of theinvention.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method of routing a call in a packet network, comprising:attempting to establish the call to a destination endpoint; detecting,by a processor, a failure condition for the destination endpoint for thecall, wherein the failure condition causes the destination endpoint tobe unable to perform its intended function, wherein the detectingcomprises: identifying an unavailability of the destination endpoint;and determining the unavailability of the destination endpoint betweenan error condition and a non-error condition based upon a failure toreceive a busy/no answer message in response to a call setup message;wherein the failure condition is detected only in response to theunavailability of the destination endpoint due to the error condition;identifying an alternative endpoint address from an alternative routingplan registered with the packet network only in response to the failurecondition due to the error condition, wherein the alternative endpointaddress is not identified for the non-error condition, wherein theidentifying of the alternative endpoint address comprises: notifying anapplication server coupled to a database configured to store alternaterouting plans for a plurality of endpoints; and receiving thealternative endpoint address from the application server that wasobtained by the application server by querying the database in responseto the notifying; and routing the call to the alternative endpointaddress.
 2. The method of claim 1, wherein the identifying of thealternative endpoint address further comprises: querying the databaseusing the destination endpoint as an index value.
 3. The method of claim1, wherein the failure condition is detected by a network element in thepacket network.
 4. The method of claim 1, wherein the call is routed tothe alternative endpoint address by a network element in the packetnetwork.
 5. The method of claim 1, wherein the packet network comprisesa voice-over-internet protocol network.
 6. An apparatus for routing acall in a packet network, comprising: a processor; and acomputer-readable medium in communication with the processor, whereinthe computer-readable medium has stored thereon a plurality ofinstructions, the plurality of instructions including instructionswhich, when executed by the processor, cause the processor to performoperations, the operations comprising: attempting to establish the callto a destination endpoint; detecting a failure condition for thedestination endpoint for the call, wherein the failure condition causesthe destination endpoint to be unable to perform its intended function,wherein the detecting comprises: identifying an unavailability of thedestination endpoint; and determining the unavailability of thedestination endpoint between an error condition and a non-errorcondition based upon a failure to receive a busy/no answer message inresponse to a call setup message; wherein the failure condition isdetected only in response to the unavailability of the destinationendpoint due to the error condition; identifying an alternative endpointaddress from an alternative routing plan registered with the packetnetwork only in response to the failure condition due to the errorcondition, wherein the alternative endpoint address is not identifiedfor the non-error condition, wherein the identifying the alternativeendpoint address comprises: notifying an application server coupled to adatabase configured to store alternate routing plans for a plurality ofendpoints; and receiving the alternative endpoint address from theapplication server that was obtained by the application server byquerying the database in response to the notifying; and routing the callto the alternative endpoint address.
 7. The apparatus of claim 6,wherein the operations further comprise: querying the database using thedestination endpoint as an index value.
 8. The apparatus of claim 6,wherein the detecting is performed by a network element in the packetnetwork.
 9. The apparatus of claim 6, wherein the routing is performedby a network element in the packet network.
 10. The apparatus of claim6, wherein the packet network comprises a voice-over-internet protocolnetwork.
 11. A tangible computer readable storage medium having storedthereon instructions that, when executed by a processor, cause theprocessor to perform operations of routing a call in a packet network,the operations comprising: attempting to establish the call to adestination endpoint; detecting a failure condition for the destinationendpoint for the call, wherein the failure condition causes thedestination endpoint to be unable to perform its intended function,wherein the detecting comprises: identifying an unavailability of thedestination endpoint; and determining the unavailability of thedestination endpoint between an error condition and a non-errorcondition based upon a failure to receive a busy/no answer message inresponse to a call setup message; wherein the failure condition isdetected only in response to the unavailability of the destinationendpoint due to the error condition; identifying an alternative endpointaddress from an alternative routing plan registered with the packetnetwork only in response to the failure condition due to the errorcondition, wherein the alternative endpoint address is not identifiedfor the non-error condition, wherein the identifying of the alternativeendpoint address comprises: notifying an application server coupled to adatabase configured to store alternate routing plans for a plurality ofendpoints; and receiving the alternative endpoint address from theapplication server that was obtained by the application server byquerying the database in response to the notifying; and routing the callto the alternative endpoint address.
 12. The tangible computer readablestorage medium of claim 11, wherein the identifying of the alternativeendpoint address further comprises: querying the database using thedestination endpoint as an index value.
 13. The tangible computerreadable storage medium of claim 11, wherein the packet networkcomprises an internet protocol network.
 14. The tangible computerreadable storage medium of claim 13, wherein the packet networkcomprises a services-over-internet protocol network.
 15. The tangiblecomputer readable storage medium of claim 14, wherein the packet networkcomprises a voice-over-internet protocol network.
 16. The tangiblecomputer readable storage medium of claim 11, wherein the detecting, theidentifying, and the routing are performed for each additional call.